1. Field of the Invention
The present invention relates generally to valves for use in the fluid circuits of refrigeration and air conditioning systems and, more particularly, to ball valves used as compressor valves, line service valves or expansion valves, incorporating means to achieve incremental valve actuation.
2. Discussion
To significantly improve the overall energy efficiency of a refrigeration or air conditioning system and to minimize the unwanted release of refrigerant from the fluid circuit to atmosphere, it has been considered important to be able to remotely control the actuation, including incremental actuation, of system components, including compressor valves, line service valves and expansion valves.
To this end, modest attempts have been made to design remotely controlled or actuated valves for use in the fluid circuits of refrigeration and air conditioning systems.
One example of an actuated valve which has seen widespread use in the refrigeration and air conditioning industry for remotely controlling the flow of refrigerant through a fluid circuit is a solenoid-operated globe-type valve and is generally illustrated in prior art FIG. 1.
The valve 200 includes a body member 202 having a first and a second fluid passage 204, 206 running therethrough which, when combined, provide a fluid passage through the entire valve 200. Standard fluid fittings 208 located at the ends of the first and second fluid passages 204, 206 enable the valve 200 to be easily installed in a fluid circuit. Disposed between the first and second fluid passages 204, 206 at an upper portion 210 of the body member 202 is a solenoid 212. The solenoid 212 is affixed to the body member 202 by any of several suitable means, such as welding, brazing or soldering, as generally indicated at 214, or with a threaded connection. The solenoid 212 includes a plunger operator 216 which is disposed for linear movement within the valve body 202 upon energization of the solenoid 212. At one end of the plunger operator 216 is a globe type plug or closure element 218 that is operable to completely shut off the fluid passage 204 when in the closed position. A spring member 220 is placed about the plunger operator 216 and biased against the closure element 218. The plunger operator 216 is linearly positionable between a closed position (not shown) and an opened position (as shown in FIG. 1) when the solenoid 212 is energized from its de-activated state. In the opened position, the closure element 218 is withdrawn from the valve seat 222 by the electromagnetic force generated in the solenoid 212, overcoming the bias of the spring member 220. Fluid is then free to flow through the fluid passages 204, 206 of the valve as indicated by arrows 224. In the closed position, the solenoid 212 is deactivated and the biasing force of the spring member 220 causes the closure element 218 to advance into the fluid passage 204 and into engagement against the valve seat 222. When closed, fluid flow through the valve 200 is prohibited.
It is significant to note that, as illustrated in FIG. 1, even when the valve is in the opened position, the closure element of the solenoid valve remains at least partially protruding into the fluid flow stream. Because of this inherent design feature, blockage or interference within the fluid passage is created and, the fluid flow through the valve becomes turbulent, resulting in an increased pressure drop across the valve. The pressure drop, in turn, reduces the efficiency of the valve by allowing a significant amount of energy to be lost from the refrigeration circuit. Consequently, this energy loss presents a design constraint that must be addressed by refrigeration and air conditioning system designers and engineers as they develop refrigeration and air conditioning systems. Often, to compensate for the energy loss, system designers and engineers specify larger, over-sized compressors which exceed the thermodynamic requirements of the refrigeration system application. The use of such oversized compressors is inefficient and a waste of energy.
Solenoid-actuated valves which have been used in the prior art also present other difficulties. One problem results from the fact that there is no control over the speed at which the valve is closed because the switching of the valve between its opened and closed positions occurs nearly instantaneously. As such, the potential exists for the creation of a detrimental condition within the fluid circuit known as a "fluid hammer" effect. When a valve is closed too quickly, a "fluid hammer" caused by the force of the moving fluid against the closure element, can create a significant, momentary spike in the fluid pressure within the valve, often times substantially exceeding the pressure capacity for the valve. In many cases, cracks or breaks which are brought on in the fluid lines by a fluid hammer result in the undesirable loss of refrigerant to atmosphere. In some extreme situations, the fluid hammer effect could cause the valve, itself, to break apart creating an undesirable result.
Also, solenoid-actuated valves typically require a considerable draw of electrical current for their operation. As can be readily appreciated, the closure element of the solenoid-actuated valve must be sufficiently biased by the spring member in order to overcome the force of the pressurized fluid in the circuit and to engage the valve seat to prohibit the flow of fluid through the valve. In turn, the electromagnetic force generated by the solenoid must overcome the spring bias in order to open the valve. This requires that a sufficient amount of electrical energy be received at the solenoid from a remote power source. The amount of energy necessary to operate a solenoid-actuated valve of this type is on the order of 10-12 amps.
Consequently, any efficiency gains to the fluid circuit that are attributable to remote control of the solenoid-actuated valve are more than offset by the efficiency reductions due to the inherent energy losses resulting from flow turbulence and substantial pressure drop across the globe-type valve, the increased operating costs associated with the cost of the valve as well as with the energy required for operation of the valve and, finally, the concerns that could be generated as a result of the occurrence of the "fluid hammer" effect.
For these reasons, ball valves are generally preferred for applications in refrigeration and air conditioning fluid circuits because, among other advantages, they exhibit high efficiency fluid flow characteristics and they allow some degree of control over the speed at which the valve is closed. However, the ball valves used in refrigeration and air conditioning systems today, including compressor valves and line service valves, are primarily (if not exclusively) manually operated.
Attempts have also been made to design a remotely controlled, actuated ball valve for use in refrigeration and air conditioning systems. However, no mechanism for the efficient, controlled actuation of a ball valve disposed within a fluid circuit has, as yet, been embraced by the refrigeration and air conditioning industry.
One prior art actuated ball valve comprised an electric, motor-driven actuation mechanism employing a worm gear. The worm gear, in turn, drove a pinion connected to a stem operator of the ball valve. A limit switch controlling the revolutions of the motor (and worm gear) consequently controlled the rotation of the ball valve between the opened position and the closed position. However, this type of actuated ball valve has not received widespread acceptance in the refrigeration and air conditioning industry for several reasons. One reason is that the amount of torque required to cycle the ball valve between the opened and closed positions necessitates an electric motor having a high amperage electrical draw (e.g. on the order of 15 amps), thereby significantly increasing the power requirements for actuation of the valve. In addition, because the components of these prior actuated ball valves were not optimally designed to operate with one another, additional components were necessary to interface a controller to the actuation unit, increasing the cost and complexity of the actuated valve. In short, such prior art actuated ball valves are cost prohibitive.
It is, therefore, an objective of the present invention to provide a ball valve for use in the fluid circuit of a refrigeration or air conditioning system, that provides an efficient and cost effective means for controlling the incremental actuation of the ball valve.
It is another objective of the present invention to provide such an actuated ball valve that exhibits significantly improved fluid flow over prior art actuated valves.
It is still another objective of the present invention to provide such an actuated ball valve which reduces or eliminates the potential for creating the "fluid hammer" effect within the fluid circuit.
It is a further objective of the present invention to provide such an actuated ball valve which harnesses the power of the pressurized refrigerant in the fluid circuit as the primary power medium to achieve valve actuation.
It is yet an additional objective of the present invention to provide such an actuated ball valve which can be directly coupled to a remote control system, such as a microprocessor, which generates control signals on the order of milli-amps.